Design,synthesis, and biological evaluation of resveratrol analogues as aromatase and quinone reductase 2 inhibitors for chemoprevention of cancer

A series of new resveratrol analogues were designed and synthesized and their inhibitory activities against aromatase were evaluated. The crystal structure of human aromatase (PDB 3eqm) was used to rationalize the mechanism of action of the aromatase inhibitor 32 (IC₅₀ 0.59 μM) through docking, molecular mechanics energy minimization, and computer graphics molecular modeling, and the information was utilized to design several very potent inhibitors, including compounds 82 (IC₅₀ 70 nM) and 84 (IC₅₀ 36 nM). The aromatase inhibitory activities of these compounds are much more potent than that for the lead compound resveratrol, which has an IC₅₀ of 80 μM. In addition to aromatase inhibitory activity, compounds 32 and 44 also displayed potent QR2 inhibitory activity (IC₅₀ 1.7 μM and 0.27 μM, respectively) and the high-resolution X-ray structures of QR2 in complex with these two compounds provide insight into their mechanism of QR2 inhibition. The aromatase and quinone reductase inhibitors resulting from these studies have potential value in the treatment and prevention of cancer.     

Synthesis and topoisomerases inhibitory activity of heteroaromatic chalcones

The critical role of nuclear topoisomerase enzymes during cell proliferation process guided topoisomerases to be one of the major targets for anticancer drug development. We have designed and synthesized 22 heteroaromatic ring incorporated chalcone derivatives substituted with epoxide or thioepoxide. Topoisomerase enzyme inhibitory activity and cytotoxic tests were also conducted to evaluate compounds’ pharmacological efficacy. In the topoisomerase I inhibitory test, compound 1 was most active one, 24% of inhibition at 20 μM, among all the compounds but it was lower than camptothecin. Compounds 9, 11, and 13 inhibited the function of topoisomerase II more strongly than etoposide with almost same magnitude (around 90% and 30% inhibition at 100 and 20 μM, respectively) which were higher than those of etoposide (72% and 18% inhibition). In the cytotoxicity test, compound 9 inhibited T47D cancer cell growth with the IC₅₀ value of 6.61 ± 0.21 μM. On the other hand, compound 13 (IC₅₀: 4.32 ± 0.18 μM) effectively suppressed MDA-MB468 cancer cell growth.     

New class of alkynyl glycoside analogues as tyrosinase inhibitors

A new series of alkynyl glycoside analogues were designed and synthesized from cheap and a commercially available sugar by introduction of various alkynyl and alkyl groups at C-1 and C-6 positions of the sugar ring. The inhibitory abilities of alkynyl glycosides were investigated in vitro on mushroom tyrosinase for the catalysis of l-Tyrosine and l-DOPA as substrates and comparing with arbutin and kojic acid. Non-terminal alkyne compound 2d showed excellent tyrosinase inhibitory activity (IC₅₀ 54.0 μM) against l-Tyrosine comparable to arbutin (IC₅₀ 1.46 mM) while 2b exhibited potent activities (IC₅₀ 34.3 μM) against L-DOPA higher than kojic acid (IC₅₀ 0.11 mM) and arbutin (IC₅₀ 13.3 mM). Kinetic studies revealed that compound 2d was a non-competitive inhibitor with the best Ki value of 21 μM and formed an irreversible receptor complex with mushroom tyrosinase. The SARs results showed that the type of alkyne and alkyl groups at position C-6 on sugar and the stereoisomer played an important role in determining their inhibitory activities. The potent activity of alkynyl glycosides identified in this study highlight the importance of this scaffold and these compounds are very modestly potent to the development of new class for tyrosinase inhibitor.     

Pyridoxine-resveratrol hybrids Mannich base derivatives as novel dual inhibitors of AChE and MAO-B with antioxidant and metal-chelating properties for the treatment of Alzheimer’s disease

A series of pyridoxine-resveratrol hybrids Mannich base derivatives as multifunctional agents have been designed, synthesized and evaluated for cholinesterase (ChE) and monoamine oxidase (MAO) inhibitory activity. To further explore the multifunctional properties of the new derivatives, their antioxidant activities and metal-chelating properties were also tested. The results showed that most of these compounds could selectively inhibit acetylcholinesterase (AChE) and MAO-B. Among them, compounds 7d and 8b exhibited the highest potency for AChE inhibition with IC₅₀ values of 2.11 μM and 1.56 μM, respectively, and compound 7e exhibited the highest MAO-B inhibition with an IC₅₀ value of 2.68 μM. The inhibition kinetic analysis revealed that compound 7d showed a mixed-type inhibition, binding simultaneously to the CAS and PAS of AChE. Molecular modeling study was also performed to investigate the binding mode of these hybrids with MAO-B. In addition, all target compounds displayed good antioxidant and metal-chelating properties. Taken together, these preliminary findings can be a new starting point for further development of multifunctional agents for Alzheimer’s disease.     

Discovery of new [1,4]dioxino[2,3-f]quinazoline-based inhibitors of EGFR including the T790M/L858R mutant

A novel series of 2,3-dihydro-[1,4]dioxino[2,3-f]quinazoline derivatives were designed, synthesized and evaluated as reversible and noncovalent epidermal growth factor receptor (EGFR) inhibitors. Most of the compounds exhibited good potency against EGFR^wt and some showed moderate to excellent potency against EGFR^T790M/L858R mutant. The half-maximal inhibitory concentration (IC₅₀) values of twenty-one compounds against EGFR^wt were less than 50 nM, and those of six compounds were less than 10 nM. The IC₅₀ values of eleven compounds against EGFR^T790M/L858R were less than 100 nM. Among these, compound b1 displayed the most potent inhibitory activity against EGFR^wt (IC₅₀ = 2.0 nM) and EGFR^T790M/L858R (IC₅₀ = 6.9 nM). Compounds with excellent inhibitory activities against EGFR^wt and EGFR^T790M/L858R kinase inhibitory activities showed good antiproliferative activities against H358 and A549 cells. Docking study was performed to position compound b1 into the EGFR active pocket to determine the probable binding conformation.     

Synthesis,structure-activity relationships studies of benzoxazinone derivatives as α-chymotrypsin inhibitors

A series of benzoxazinones 1–28 were synthesized via reaction of anthranilic acid with various substituted benzoyl chlorides in the presence of triethylamine in chloroform. Compounds 1–18 showed a good inhibition of α-chymotrypsin with IC₅₀ ± SEM values between 6.5 and 341.1 μM. Preliminary structure-activity relationships studies indicated that the presence of substituents on benzene ring reduces the inhibitory potential of benzoxazinone. Also the increased inhibitory potential due to fluoro group at phenyl substituent was observed followed by chloro and bromo substituents. Compounds with strong electron donating or withdrawing groups on phenyl substituent, showed a good inhibitory potential at ortho > meta > para position. Kinetics studies showed diverse types of inhibition, except uncompetitive-type inhibition. The Ki values ranged between 4.7 and 341.2 μM. Interestingly, most of these compounds were non-cytotoxic to 3T3 cell line at 30 μM, except compounds 6, 14 and 15. Competitive inhibitors of chymotrypsin are like to inhibit other α-chymotrypsin-like serine proteases due to structural and functional similarities between them. The inhibitors identified during the current study deserve to be further studied for their therapeutic potential against abnormalities mediated by chymotrypsin or other serine protease.     

Synthesis and evaluation of naphthoflavones as a new class of non purine xanthine oxidase inhibitors

In view of reported xanthine oxidase inhibitory potential of naphthopyrans and flavones, naphthoflavones as hybrids of the two were designed, synthesized and evaluated for in vitro xanthine oxidase inhibitory activity in the present study. The results of the assay revealed that the naphthoflavones possess promising inhibitory potential against the enzyme with IC₅₀ values ranging from 0.62 to 41.2 μM. Structure activity relationship indicated that the nature and placement of substituents on the phenyl ring at 2nd position remarkably influences the inhibitory activity. Substitution of halo and nitro groups at ortho and para position of the phenyl ring (2nd position) remarkably favored the activity. NF-4 with p-fluoro phenyl ring was the most potent inhibitor with IC₅₀ value of 0.62 μM. Enzyme kinetics study was also performed to investigate the inhibition mechanism and it was found that the naphthoflavones displayed mixed type inhibition. The basis of significant inhibition of xanthine oxidase by NF-4 was rationalized by molecular modeling studies.     

Design,synthesis and biological evaluation of novel tripeptidyl epoxyketone derivatives constructed from β-amino acid as proteasome inhibitors

A series of novel tripeptidyl epoxyketone derivatives constructed from β-amino acid were designed, synthesized and evaluated as proteasome inhibitors. All target compounds were tested for their proteasome inhibitory activities and selected compounds were tested for their anti-proliferation activities against two multiple myeloma (MM) cell lines RPMI 8226 and NCI-H929. Among them, eleven compounds exhibited proteasome inhibitory rates of more than 50% at the concentration of 1 μg/mL and nine compounds showed anti-proliferation activities with IC₅₀ values at low micromolar level. Compound 20h displayed the most potent proteasome inhibitory activities (IC₅₀: 0.11 ± 0.01 μM) and anti-proliferation activities with IC₅₀ values at 0.23 ± 0.01 and 0.17 ± 0.02 μM against two tested cell lines. Additionally, the poly-ubiquitin accumulation in the western blot analysis supported that proteasome inhibition in a cellular system was induced by compound 20h. All these experimental results confirmed that β-amino acid can be introduced as a building block for the development of proteasome inhibitors.     

Synthesis,in vitro ADME profiling and in vivo pharmacological evaluation of novel glycogen phosphorylase inhibitors

A small set of indole-2-carboxamide derivatives identified from a high-throughput screening campaign has been described as a novel, potent, and glucose-sensitive inhibitors of glycogen phosphorylase a (GPa). Among this series of compounds, compound 2 exhibited moderate GP inhibitory activity (IC₅₀ = 0.29 μM), good cellular efficacy (IC₅₀ = 3.24 μM for HepG2 cells and IC₅₀ = 7.15 μM for isolated rat hepatocytes), together with good absorption, distribution, metabolism, and elimination (ADME) profiles. The in vivo animal study revealed that compound 2 significantly inhibited an increase of fasting blood glucose level in adrenaline-induced diabetic mice.     

Design,synthesis and biological evaluation of novel pyrimidine, 3-cyanopyridine and m-amino-N-phenylbenzamide based monocyclic EGFR tyrosine kinase inhibitors

36 new compounds with the typical skeleton of 4-anilino-5-vinyl/ethynyl pyrimidine, 4-anilino-3-cyano-5-vinyl/ethynyl/phenyl pyridine, and m-amino-N-phenylbenzamide, are designed, synthesized and selectively tested on EGFR, ErbB-2 kinases, and A-549, HL60 cells growth inhibition. Results from the bioactivity and chemical structures yield preliminary structure–activity relationships (SARs). The most potent 5-ethynylpyrimidine derivative 20a has an IC₅₀ value of 45 nM to EGFR kinase. Several compounds of other series also show IC₅₀ values <1 μM for EGFR and <5 μM for A-549 and HL60 cells growth inhibition.     

Synthesis and evaluation of novel triazoles and mannich bases functionalized 1,4-dihydropyridine as angiotensin converting enzyme (ACE) inhibitors

A series of novel diethyl 2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate embedded triazole and mannich bases were synthesized, and evaluated for their angiotensin converting enzyme (ACE) inhibitory activity. Screening of above synthesized compounds for ACE inhibition showed that triazoles functionalized compounds have better ACE inhibitory activity compared to that of mannich bases analogues. Among all triazoles we found 6h, 6i and 6j to have good ACE inhibition activity with IC₅₀ values 0.713 μM, 0.409 μM and 0.653 μM, respectively. Among mannich bases series compounds, only 7c resulted as most active ACE inhibitor with IC₅₀ value of 0.928 μM.     

Synthesis and aromatase inhibitory activity of some new 16E-arylidenosteroids

A new series of 16E-arylidene androstene derivatives has been synthesized and evaluated for aromatase inhibitory activity. The impact of various aryl substituents at 16 position of the steroid skeleton on aromatase inhibitory activity has been observed. The 16E-arylidenosteroids 6, 10 and 11 exhibited significant inhibition of the aromatase enzyme. 16-(4-Pyridylmethylene)-4-androstene-3,17-dione (6, IC₅₀: 5.2 μM) and 16-(benzo-[1,3]dioxol-5-ylmethylene)androsta-1,4-diene-3,17-dione (11, IC₅₀: 6.4 μM) were found to be approximately five times more potent in comparison to aminoglutethimide.     

Synthesis and antiproliferative evaluation of piperazine-1-carbothiohydrazide derivatives of indolin-2-one

By varying the substituents (R¹) at the indolin-2-one scaffold, a series of indolin-2-one derivatives bearing 4-phenylpiperazine-1-carbothiohydrazide moiety at the C3-position were synthesized and evaluated for their antiproliferative activity against three human cancer cell lines. We further selected the 5-chloroindolin-2-one moiety for the extension to another series of compounds by varying the substituents (R²) at the phenyl group connected with the piperazine ring. Among all the compounds synthesized, 6d and 6l were most potent with IC₅₀ values of 3.59 and 5.58 μM, respectively against A549 lung cancer cells, while 5f and 6l possessed IC₅₀ values of 3.49 and 4.57 μM, respectively against HCT-116 colon cancer cells which were comparable to that of Sunitinib, an indolin-2-one derivative in cancer therapy.     

Studies on depigmenting activities of dihydroxyl benzamide derivatives containing adamantane moiety

Six diphenolic compounds containing adamantane moiety were synthesized and evaluated as potent inhibitors on tyrosinase activity and melanin formation in melan-a cells. The inhibitory activity of 4-adamantyl resorcinol 1 was similar to that of 4-n-butyl resorcinol in both assays. However, dihydroxyl benzamide derivatives 6a–e showed different inhibitory patterns. All derivatives significantly suppressed the cellular melanin formation without tyrosinase inhibitory activities. These behaviors indicated that the introduction of amide bond changes the binding mode of dihydroxyl groups to tyrosinase. Among derivatives, 6d (3,4-dihydroxyl compound) and 6e (2,3-dihydroxyl compound) showed stronger inhibitory activities (IC₅₀ = 1.25 μM and 0.73 μM, respectively) as compared to 4-n-butyl resorcinol (IC₅₀ = 21.64 μM) and hydroquinone (IC₅₀ = 3.97 μM). This study showed that the position of dihydroxyl substituent at aromatic ring is important for the intercellular inhibition of melanin formation, and also amide linkage and adamantane moiety enhance the inhibition.     

Benzophenone C-glucosides and gallotannins from mango tree stem bark with broad-spectrum anti-viral activity

The high mutation rate of RNA viruses has resulted in limitation of vaccine effectiveness and increased emergence of drug-resistant viruses. New effective antivirals are therefore needed to control of the highly mutative RNA viruses. The n-butanol fraction of the stem bark of Mangifera indica exhibited inhibitory activity against influenza neuraminidase (NA) and coxsackie virus 3C protease. Bioassay guided phytochemical study of M. indica stem bark afforded two new compounds including one benzophenone C-glycoside (4) and one xanthone dimer (7), together with eleven known compounds. The structures of these isolated compounds were elucidated on the basis of spectroscopic evidences and correlated with known compounds. Anti-influenza and anti-coxsackie virus activities were evaluated by determining the inhibition of anti-influenza neuraminidase (NA) from pandemic A/RI/5+/1957 H2N2 influenza A virus and inhibition of coxsackie B3 virus 3C protease, respectively. The highest anti-influenza activity was observed for compounds 8 and 9 with IC₅₀ values of 11.9 and 9.2 μM, respectively. Compounds 8 and 9 were even more potent against coxsackie B3 virus 3C protease, with IC₅₀ values of 1.1 and 2.0 μM, respectively. Compounds 8 and 9 showed weak cytotoxic effect against human hepatocellular carcinoma and human epithelial carcinoma cell lines through MTT assay.     

Toward discovery of mutant EGFR inhibitors; Design,synthesis and in vitro biological evaluation of potent 4-arylamino-6-ureido and thioureido-quinazoline derivatives

A new series of 4-anilinoquinazolines with C-6 ureido and thioureido side chains and various substituents at the C-4 anilino moiety was designed, synthesized and evaluated as wild type (WT) and mutant EGFR inhibitors. Most of the compounds inhibited EGFR kinase wild type (EGFR WT) with IC₅₀ values in the low nanomolar range (<0.495–9.05 nM) and displayed more potent cytotoxic effect in BaF/3 expressing EGFR WT than reference compound gefitinib. The anti-proliferative effect of all synthesized compounds against gefitinib insensitive double mutant cell lines Ba/F3 expressing Del19/T790M and Ba/F3 expressing L858R/T790M were assayed. Compounds 4d, 6f, 7e showed significant inhibition (IC₅₀ = 1.76–2.38 μM) in these mutant lines and significant Her2 enzyme inhibition (IC₅₀ = 19.2–40.6 nM) compared to lapatinib (60.1 nM). The Binding mode of compounds 6d, 6f, 7a, 7b and 8b were demonstrated. Furthermore, growth inhibition against gefitinib insensitive cell lines PC9-GR4 (Del19/T790M) were tested, compounds 6f and 7e showed about eight and three folds respectively greater potency than gefitinib. Our structure–activity relationships (SAR) studies suggested that presence of ethyl piperidino urea/thiourea at 6-position and bulky group of (3-chloro-4-(3-fluorobenzyloxy)phenyl)amino at 4-position of quinazoline may serve as promising scaffold for developing inhibitors against wild type and mutant EGFR.     

Synthesis,SAR, and X-ray structure of tricyclic compounds as potent FBPase inhibitors

With the aim of discovering a novel class of fructose-1,6-bisphosphatase (FBPase) inhibitors, a series of compounds based on tricyclic scaffolds was synthesized. Extensive SAR studies led to the finding of 8l with an IC₅₀ value of 0.013 μM against human FBPase. An X-ray crystallographic study revealed that 8l bound at AMP binding sites of human liver FBPase with hydrogen bonding interactions similar to AMP.     

Synthesis,biological evaluations and computational studies of N-(3-(-2-(7-Chloroquinolin-2-yl)vinyl) benzylidene)anilines as fungal biofilm inhibitors

In the present investigation, new chloroquinoline derivatives bearing vinyl benzylidene aniline substituents at 2nd position were synthesized and screed for biofilm inhibitory, antifungal and antibacterial activity. The result of biofilm inhibition of C. albicans suggested that compounds 5j (IC₅₀ value?=?51.2?μM) and 5a (IC₅₀ value?=?66.2?μM) possess promising antibiofilm inhibition when compared with the standard antifungal drug fluconazole (IC₅₀?=?40.0?μM). Two compounds 5a (MIC?=?94.2?μg/mL) and 5f (MIC?=?98.8?μg/mL) also exhibited good antifungal activity comparable to standard drug fluconazole (MIC?=?50.0?μg/mL). The antibacterial screening against four strains of bacteria viz. E. coli, P. aeruginosa, B. subtilis, and S. aureus suggested their potential antibacterial activity and especially all the compounds except 5g were found more active than the standard drug ciprofloxacin against B. subtilis. To further gain insights into the possible mechanism of these compounds in biofilm inhibition through the agglutinin like protein (Als), molecular docking and molecular dynamics simulation studies were carried out. Molecular modeling studies suggested the clear role in inhibition of this protein and the resulting biofilm inhibitory activity.     

Relationships between the structure of 6-allyl-6,8-diazabicyclo[3.2.2]nonane derivatives and their σ receptor affinity and cytotoxic activity

A series of bridged piperazine derivatives was prepared and the affinity toward σ₁ and σ₂ receptors by means of radioligand binding assays as well as the inhibition of the growth of six human tumor cell lines was investigated. All possible stereoisomers of the 2-hydroxy, 2-methoxy, 2,2-dimethoxy, 2-oxo, and 2-unsubstituted 6,8-diazabicyclo[3.2.2]nonanes were prepared in a chiral pool synthesis starting with (S)- and (R)-glutamate. A Dieckmann analogous cyclization was the key step in the synthesis of the bicyclic framework. The configuration in position 2 was established by a diastereoselective LiBH₄ reduction and subsequent Mitsunobu inversion. Structure–affinity relationships demonstrate that substituents in position 2 decrease σ₁ receptor affinity which might be due to unfavorable interactions with the σ₁ receptor protein. Without a substituent in position 2 high σ₁ affinity was obtained (23a ((+)-(1S,5S)-6-allyl-8-(4-methoxybenzyl)-6,8-diazabicyclo[3.2.2]nonane): K_i = 11 nM). Experiments with six human tumor cell lines showed a weak but selective growth inhibition of the human small cell lung cancer cell line A-427 by the methyl ethers ent-16b (IC₅₀ = 18.9 μM), 21a (IC₅₀ = 16.4 μM), ent-21a (IC₅₀ = 20.4 μM), and 21b (IC₅₀ = 27.1 μM) and the unsubstituted compounds 23a and 23b (42% inhibition at 20 μM).     

Synthesis and α-glucosidase inhibitory activity evaluation of N-substituted aminomethyl-β-d-glucopyranosides

A series of N-substituted 1-aminomethyl-β-d-glucopyranoside derivatives was prepared. These novel synthetic compounds were assessed in vitro for inhibitory activity against yeast α-glucosidase and both rat intestinal α-glucosidases maltase and sucrase. Most of the compounds displayed α-glucosidase inhibitory activity, with IC₅₀ values covering the wide range from 2.3 μM to 2.0 mM. Compounds 19a (IC₅₀ = 2.3 μM) and 19b (IC₅₀ = 5.6 μM) were identified as the most potent inhibitors for yeast α-glucosidase, while compounds 16 (IC₅₀ = 7.7 and 15.6 μM) and 19e (IC₅₀ = 5.1 and 10.4 μM) were the strongest inhibitors of rat intestinal maltase and sucrase. Analysis of the kinetics of enzyme inhibition indicated that 19e inhibited maltase and sucrase in a competitive manner. The results suggest that the aminomethyl-β-d-glucopyranoside moiety can mimic the substrates of α-glucosidase in the enzyme catalytic site, leading to competitive enzyme inhibition. Moreover, the nature of the N-substituent has considerable influence on inhibitory potency.